System and method for multi-resolution storage of images

ABSTRACT

A data-storage method includes capturing video data, identifying an object of which a high-resolution image is desired, the object being represented by a subset of the captured video data, compressing, to a first resolution, the subset of the captured video data, and compressing, to a second resolution, data of the captured video data other than the subset of the captured video data. According to the method, the first resolution is greater than the second resolution. The method further includes storing the compressed video data.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority from, and incorporates by reference for any purpose the entire disclosure of, U.S. Provisional Patent Application No. 61/029,101, filed Feb. 15, 2008. In addition, this patent application claims priority from and incorporates by reference U.S. Provisional Patent Application No. 61/029,092, also filed Feb. 15, 2008. This patent application also incorporates by reference U.S. Patent Application Publication No. 2006/0158968, filed on Oct. 12, 2005, and a patent application filed on the same date as this patent application and bearing Docket No. 47565-P007US.

BACKGROUND

1. Technical Field

This patent application relates generally to video surveillance, and in particular, to systems and methods for multi-resolution storage of images.

2. Background

Many law-enforcement vehicles include a video camera to capture video of activities transpiring both outside and inside the vehicle. One use of the video captured by these video cameras is as evidence in a criminal trial. In order for these videos to be used as evidence, the images must be clearly identifiable by, for example, a jury or an expert witness. Often the law-enforcement vehicles and their video recording devices remain in use for extended periods of time, for example, when an officer stays out all night on patrol. It is therefore often necessary to compress the video being recorded in order to be able to store large volumes of data.

SUMMARY OF THE INVENTION

A data-storage method includes capturing video data, identifying an object of which a high-resolution image is desired, the object being represented by a subset of the captured video data, compressing, to a first resolution, the subset of the captured video data, and compressing, to a second resolution, data of the captured video data other than the subset of the captured video data. According to the method, the first resolution is greater than the second resolution. The method further includes storing the compressed video data.

An article of manufacture for data storage includes at least one computer readable medium and processor instructions contained on the at least one computer readable medium. The processor instructions are configured to be readable from the at least one computer readable medium by at least one processor and thereby cause the at least one processor to operate as to capture video data and identify an object of which a high-resolution image is desired, the object being represented by a subset of the captured video data. The processor instructions are further configured to cause the at least one processor to operate as to compress, to a first resolution, the subset of the captured video data, and compress, to a second resolution, data of the captured video data other than the subset of the captured video data. According to the article of manufacture, the first resolution is greater than the second resolution. The processor instructions are further configured to cause the at least one processor to operate as to store the compressed video data.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of various embodiments of the present invention may be obtained by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings, wherein:

FIG. 1 is a schematic diagram of a system for capturing and storing video data;

FIG. 2 is a flow chart illustrating a process for compressing and storing video data;

FIG. 3 is an illustrative view of a video-data image; and

FIG. 4 illustrates a system for capturing and storing video data.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Various embodiments of the present invention will now be described more fully with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, the embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

In a typical embodiment, pixels of a video stream coming from a video camera in a vehicle such as, for example, a law-enforcement vehicle may contain both chroma (color information) and luma (brightness or black and white information). Most of the resolution may be contained in the black and white information of the video stream, even though the images may be color images. Between the luma and chroma information, the luma may contain much of the information relative to how much detail in the video stream is visible.

In order to store over long periods of time a typically large amount of video data captured by the video camera, data-compression algorithms are often used to compress the video data. In a typical embodiment, the video data may be, for example, still images or motion video. There are various data-compression algorithms currently in use for compressing video data. The data-compression algorithms may include, for example, lossless algorithms and lossy algorithms. Lossless algorithms are a class of data-compression algorithms that allow a replica of original data to be reconstructed from compressed data. In contrast, lossy algorithms are a class of data-compression algorithms that allow an approximation of the original data to be reconstructed in exchange for a better data-compression rate. In a lossy algorithm, some visual quality is lost in the data-compression process, which lost visual quality cannot be restored. Data-compression algorithms typically utilize a combination of techniques for compressing, for example, video data. The combination of techniques for compressing the video data may include, for example, downsampling or subsampling, block splitting, pixelating, and/or lessening resolution.

A few examples of data-compression algorithms include the MPEG family of algorithms such as, for example, MPEG 2 and MPEG 4. Almost all data-compression algorithms lessen the clarity and sharpness of the compressed video data, making, for example, facial features, letters, and numbers more difficult to identify. Because clarity is often critical in police work such as, for example, in identifying a particular vehicle or suspect to a jury, it is important that the images remain sufficiently clear even after the video data has been compressed. For example, when video of a traffic stop is recorded, it is important that the clarity, for example, of a license plate of the vehicle remain uncompromised so that letters and numbers of the license plate are identifiable.

In a typical embodiment, some cameras may, for example, capture video data at approximately 480 horizontal lines while the video data may be recorded at, for example, 86 horizontal lines. The resolution of the video data being recorded may be, for example, one fourth the resolution of what the camera actually captured. By accessing the video data while the video data is still at a maximal (i.e., uncompressed) resolution, effects of data-compression algorithms and recording on the readability of, for example, license plates and other objects can be minimized.

FIG. 1 is a schematic diagram of a system 100 for capturing and storing video data. The system 100 includes an image-capture device 102 for capturing raw video data. The image-capture device 102 may, for example, be located at various locations within or on a police vehicle. In a typical embodiment, the image-capture device 102 may, for example, be located on a front console of the law-enforcement vehicle in order to capture areas of interest outside of the law-enforcement vehicle. In a typical embodiment, the image-capture device 102 is a digital video camera. The system 100 further includes a buffer 104 interoperably connected to the image-capture device 102. The captured raw video data is transmitted by the image-capture device 102 to the buffer 104. The buffer 104 is used for temporary storage of the raw video data.

The system 100 also includes a zoom-area locator 106. The zoom-area locator 106 is adapted to find coordinates corresponding to a subset of the raw video data that pertains to one or more areas of interest. In a typical embodiment, an area of interest may be, for example, a vehicle license plate, facial features of an individual, or any other items that require retention at higher resolution levels. The coordinates are transmitted from the zoom-area locator 106 to a compressor 110. In a typical embodiment, the one or more areas of interest may be, for example, one or more license plates located by a license-plate location algorithm.

In a typical embodiment, the compressor 110 is adapted to compresses video data from the one or more areas of interest at a first resolution level and areas other than the one or more areas of interest at a second resolution level. The first resolution level is often greater than the second resolution level. For example, at the first resolution level, the video data is often compressed substantially less than at the second resolution level. In some embodiments, the first resolution level may be obtained by not compressing the video data at all. The video data is stored on a storage medium 112. In a typical embodiment, the storage medium 112 uses a hard drive, DVD, or other recording medium.

In various embodiments, area(s) of interest compressed at the first resolution level may be fixed in particular position(s) within a field of view of the image-capture device 102. In some embodiments, a law-enforcement officer can, for example, point the image-capture device 102 in a particular direction to capture the area(s) of interest. For example, the law-enforcement officer may pull up behind a vehicle and steer the law-enforcement vehicle so that the fixed area captures the license plate of the vehicle. Another way of changing the field of view of the image-capture device 102 may include, for example, rotating the image-capture device 102 so that the fixed area covers an area of interest. In some embodiments, the area to be compressed at the first resolution level may be moved digitally within the field of view via a user interface. Each of the buffer 104, the compressor 110, and the storage medium 112 may be implemented using one or both of hardware and software.

In a typical embodiment, the area(s) of interest may be highlighted. For example, a thin colored line may encompass a license plate within an area of interest. In some embodiments, multiple license plates may be identified in one field of view. The license plates may, for example, be individually focused on by rotating the area being focused on among the various license plates. As each license plate is, in turn, focused on, an indicator, for example, a thin red line, may, for example, highlight the license plate being focused on. In some embodiments, a plurality of different indicators may be used. In some embodiments, a plurality of different license plates may be focused on at the same time. In various embodiments, facial features of an individual or other information may be encompassed by an area of interest.

In some embodiments, a fixed region, for example, a strip across a width of displayed video, may include the area of interest that has been compressed at the first resolution level. Oftentimes, a hood of the law-enforcement vehicle is in the field of view of the image-capture device 102. Since video of the hood does not typically need to be recorded, it may be desirable to insert the video being compressed at the first resolution level at a bottom of the field of view. Similarly, oftentimes the sky is recorded; in that case, it may be desirable to insert the strip of video across the top of the field of view where the sky is usually shown. In other embodiments, a vertical strip having more clarity may be desirable. In various embodiments, a user has the option of selecting the size and shape of the area of interest and where the images should be inserted.

In some embodiments, the video data saved on the storage device 112 may use approximately the same amount of storage space as other compressed video data. Because areas of greater resolution such as, for example, areas at the first resolution level, typically consume more data-storage space, other areas of the video data may be compressed to an even lesser resolution. For example, the hood of the law-enforcement vehicle shown, for example, along the bottom of the field of view or the sky shown, for example, along the top of the field of view may be compressed to a lesser resolution. The potentially deleterious effects of the lesser resolution is typically offset by areas of interest having been stored at greater resolution levels. In some embodiments, a plurality of areas of interest are compressed to a plurality of different levels of resolution. Similarly, in some embodiments, areas outside the areas of interest may be compressed to a plurality of different levels of resolution. Those having skill in the art will appreciate that various embodiments may use the above-described processes in conjunction with optical and/or digital zoom functions.

FIG. 2 is a flow chart illustrating a process 200 for compressing and storing video data. The process 200 begins at step 202. At step 202, an image-capture device such as, for example, a camera, captures raw video data from a field of view of the image-capture device. In a typical embodiment, the image-capture device may be mounted in a law-enforcement vehicle and adapted to capture the video data while the law-enforcement vehicle is moving and also when the law-enforcement vehicle is stopped such as, for example, during a traffic stop. From step 202, the process 200 proceeds to step 204. At step 204, the captured raw video data is sent to a buffer. At step 206, at least one area of interest in the captured and buffered video data is located. In some embodiments, the captured video data is read and an automatic license-plate locator algorithm is run to identify, for example, whether one or more license plates are present. In some embodiments, only luma information and not chroma information may be used. In other words, chroma information may be discarded and data representing luma information retained for later use, including compression. The luma information may have more resolution than the chroma information and the chroma (color) information may not be as critical for purposes of clarity, such as readability of numbers on a license plate. In various embodiments, the license-plate location algorithm runs on raw data coming from the image-capture device; however, it is also contemplated that the license-plate location algorithm can run on compressed data as well.

After the one or more areas of interest (e.g., license plates or faces) have been located at step 206, at step 208, location information relative to each of the located areas of interest is sent to a compressor. For example, the location information sent may be one or more sets of coordinates, such as, for example, coordinates corresponding to the four corners of a license plate. Information related to, for example, size of the one or more license plates may also be sent. At step 210, the location information is used during compression by a data-compression algorithm of pixels from the one or more areas of interest, for example, the areas of license plates. The data-compression algorithm compresses the area of interest less than areas other than the one or more areas of interest. In this way, the one or more areas of interest may be subsequently saved at a greater resolution level, while the other areas are saved at a lesser resolution level. At step 212, the compressed data is stored on a recording medium such as, for example, a DVD, a VHS tape, or other appropriate recording medium. At step 214, the process 200 ends.

FIG. 3 is an illustrative view of a video-data image 300. The video-data image 300 includes an area of interest 302. In the embodiment shown in FIG. 3, the area of interest 302 is located over a license plate. The area of interest 302 has been compressed less than the rest of the image, leaving the area of interest 302, for example, the license plate, clearer, while the remaining image is not as clear as the license-plate portion covered by the area of interest 302. In a typical embodiment, an automatic license-plate locator algorithm or a zoom area may be used to locate the area of interest 302 in the video-data image 300. In some embodiments, a user may move the area of interest 302 position the area of interest 302 over any user-selected area. In some embodiments, the area of interest 302 may be moved via, for example, a user interface which may be, for example, a keypad, a touch screen, a joystick, or other controller.

FIG. 4 illustrates a system 400 on which capturing and storing video data may be implemented. The system 400 includes a bus 402 for communicating information. The system 400 also includes a processor 404 coupled to the bus 402 and a main memory 406 such as, for example, a random access memory (RAM) or other dynamic storage device, coupled to the bus 402.

The system 400 also includes a read only memory (ROM) 408 connected to the bus 402 for storing, for example, static information and instructions from the processor 402. The system 400 also includes an image-capture device 410. In a typical embodiment, the image-capture device 410 is a digital video camera. In a typical embodiment, various components of the system 400 are used to compress video data from one or more areas of interest at a first resolution level and areas other than the one or more areas of interest at a second resolution level, perform zoom-area location (e.g., finding coordinates corresponding to a subset of video data that pertains to one or more areas of interest), and buffer raw video data as described above.

Although various embodiments of the method and system of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth herein. 

1. A data-storage method comprising: capturing video data; identifying an object of which a high-resolution image is desired, the object being represented by a subset of the captured video data; compressing, to a first resolution, the subset of the captured video data; compressing, to a second resolution, data of the captured video data other than the subset of the captured video data; wherein the first resolution is greater than the second resolution; and storing the compressed video data.
 2. The data-storage method of claim 1, wherein the identifying step comprises: obtaining location information corresponding to the object; and identifying the subset of the captured video data using the location information.
 3. The data-storage method of claim 1, wherein the identifying step comprises operation of a license-plate-location algorithm.
 4. The data-storage method of claim 1, wherein the identifying step is performed responsive to user input.
 5. The data-storage method of claim 1, wherein the location information comprises at least one set of coordinates.
 6. The data-storage method of claim 5, wherein the at least one set of coordinates corresponds to corners of at least one vehicular license plate.
 7. The data-storage method of claim 1, wherein the object comprises a face of an individual.
 8. The data-storage method of claim 1, wherein the identifying step is performed via a fixed area of a display.
 9. The data-storage method of claim 1, wherein the subset of the captured video data excludes chroma information.
 10. An article of manufacture for data storage, the article of manufacture comprising: at least one computer readable medium; processor instructions contained on at least one computer readable medium, the processor instructions configured to be readable from the at least one computer readable medium by at least one processor and thereby cause the at least one processor to operate as to perform the following steps: capturing video data; identifying an object of which a high-resolution image is desired, the object being represented by a subset of the captured video data; compressing, to a first resolution, the subset of the captured video data; compressing, to a second resolution, data of the captured video data other than the subset of the captured video data; wherein the first resolution is greater than the second resolution; and storing the compressed video data.
 11. The article of manufacture of claim 10, wherein the identifying step comprises: obtaining location information corresponding to the object; and identifying the subset of the captured video data using the location information.
 12. The article of manufacture of claim 10, wherein the identifying step comprises operation of a license-plate-location algorithm.
 13. The article of manufacture of claim 10, wherein the identifying step is performed responsive to user input.
 14. The article of manufacture of claim 10, wherein the location information comprises at least one set of coordinates.
 15. The article of manufacture of claim 14, wherein the at least one set of coordinates corresponds to corners of at least one vehicular license plate.
 16. The article of manufacture of claim 10, wherein the object comprises a face of an individual.
 17. The article of manufacture of claim 10, wherein the identifying step is performed via a fixed area of a display.
 18. The article of manufacture of claim 10, wherein the subset of the captured video data excludes chroma information. 